Clematismae (Ranunculaceae), a new species of C.sect.Meclatis from Xinjiang, China

Abstract Clematismae Z.Z.Yang & L.Xie, a new species of Ranunculaceae from Xinjiang, China, is described and illustrated. The new species is morphologically similar to C.orientalis and C.glauca but can be distinguished for being a less hairy plant (hairy in C.orientalis), often 2-ternate leaves (1–2-pinnate for C.orientalis and C.glauca), lanceolate to linear-lanceolate leaflets (elliptic or ovate in C.glauca), larger flowers (smaller flower in C.orientalis) and narrowly lanceolate sepals with acute to slightly attenuate apex (narrowly oblong sepals in C.orientalis and ovate to broadly lanceolate sepals in C.glauca). The new species is endemic to the southern slope of North Tianshan Mountain in Central Xinjiang. The conservation status of the species is also discussed.


Introduction
Clematis L. is one of the three most widely distributed genera in Ranunculaceae (the other two being Anemone L. and Ranunculus L.; Ziman and Keener 1989), with approximately 300 species (Fang et al. 1980, Tamura 1987, 1995, Essig 1991, Johnson 1997, Grey-Wilson 2000, Wang and Li 2005, Miikeda et al. 2006, Xie et al. 2011, Lehtonen et al. 2016, Jiang et al. 2017. The taxonomy of Clematis has attracted much attention due to its great horticultural value. Historically, this large genus had been subdivided into many infrageneric groups using different taxonomic levels by different authors (Spach 1839, Prantl 1887, Tamura 1987, 1995, Johnson 1997, Grey-Wilson 2000, Wang and Li 2005. Clematis sect. Meclatis (Spach) Baillon also known as the Orientalis group (sensu Grey-Wilson 1989 is one of the taxonomically most difficult groups in the genus, with approximately a dozen yellow-flowered species that are widely distributed in Eurasia (Grey-Wilson 1989, Brandenburg 2000, Wang 2006. Species of C. sect. Meclatis are especially common in the highlands of central Asia and the Tibetan plateau. In his recent worldwide taxonomic revision of the section, Wang (2006) used leaf shape and colour, inflorescence type and position, sepal morphology and filament shape as key characteristics for species classification and accepted 13 species in C. sect. Meclatis. However, recent molecular phylogenetic analyses did not clearly resolve this morphologically defined section and showed that species of C. sect. Meclatis, C. sect. Fruticella and other species, like C. barbellata Edgew. and C. pogonandra Maxim., were nested together (Xie et al. 2011, Lehtonen et al. 2016. Many of C. sect. Meclatis species are widely distributed and also present a wide range of morphologic variation (e.g. C. orientalis L., C. glauca Willd., C. tibetana Kuntze and C. tangutica (Maxim.) Korsh.). There are also several narrowly distributed local species with very distinctive characteristics recognised by Wang (2006) (e.g. C. sarezica Ikonnikov, C. caudigera W.T. Wang and C. corniculata W.T. Wang). Recently, a new local species belonging to C. sect. Meclatis from Iran was also reported (Habibi et al. 2014).
During field investigations in Xinjiang, a distinctive population of Clematis, clearly belonging to sect. Meclatis, was discovered on the southern slope of North Tianshan Mountain. After carefully studying specimens of C. sect. Meclatis in Xinjiang and adjacent areas, we confirmed that this plant represents a distinctive taxonomic entity and thus describe it as a new species.

Methods
Field investigations were conducted in the type locality and other areas in Xinjiang; specimens of C. sect. Meclatis were collected from Xinjiang and Gansu for morphological comparison. Furthermore, specimens of C. sect. Meclatis, deposited in PE, KUN, IBSC, BJFC, HIMC, IBK, NAS, XJA, XJBI, K, US and E were widely checked and evaluated using the relevant literature (Grey-Wilson 1989, Brandenburg 2000, Wang 2006. Morphological comparison and measurement of the specimens were carried out under a YKT5300 stereomicroscope. Newly collected specimens have been deposited in the herbaria of Beijing Forestry University (BJFC).

Taxonomy
Clematis mae Z.Z. Yang & L. Xie, sp. nov. urn:lsid:ipni.org:names:77194986-1 Figs 1, 2, 3A-C Diagnosis. The new species is most similar to C. orientalis L. and C. glauca Willd. and it can be distinguished from the latter two species by the following combinations of characteristics. Plants of the new species are less hairy than C. orientalis and, in this respect, are similar to C. glauca. The leaves of the new species are often 2-ternate, with lanceolate to linear lanceolate leaflets. Its leaflets are larger than those of C. orientalis, but narrower than those of C. glauca. The flowers are also significantly larger than those of C. orientalis and slightly larger than those of C. glauca. The sepals of the new species are also less hairy than those of C. orientalis and similar to those of C. glauca. The shape of the sepal is lanceolate and the apex is acute to slightly attenuate. In C. orientalis, the sepals are often linear, oblong and reflexed. The sepals of C. glauca are often wider than those of the new species (Table 1 Description. Woody vine. Branches slender, shallowly 6 sulcate, very sparsely puberulous. Leaves pinnate to 2-ternate, very rarely ternate, up to 16 cm in length and 13 cm in width; living leaflets dry, green or sometimes grey-green, papyraceous to chartaceous, lanceolate to linear-lanceolate, 1.8-6.5 × 0.3-0.8 cm, glabrous on the upper side, sparsely puberulous on the lower side, usually 2-3-lobed to 2-3-sect, sometimes undivided, terminal lobe lanceolate to linear-lanceolate, 0.4-0.8 cm broad, margin entire, never dentate, midrib adaxially flat or slightly prominent, abaxially clearly prominent. Cymes all axillary, (1-2-)3-flowered; peduncles 2.5-3.0 cm long, slender; bracts petiolate, leaflet-like, up to 3.5 cm long; central flower of the 3 flowered cyme without bracteole, two lateral flowers bracteolate; bracteole petiolate and leaflet-like, up to 8 mm long. Flower 3.8-5.8 cm diam.; pedicel 2.8-5.2 cm long, puberulous, upper pedicel usually densely hairy. Sepals 4, pinkish-purple outside and yellow inside, ascending, lanceolate, 18-27 × 4-6.5 mm, puberulous on both surfaces, outside margin velutinous, apex acute to slightly attenuate. Stamens more than 30, 9-12 mm long; filaments lanceolate linear, widened in the lower part, pubescent; anthers linear to narrowly oblong, 3-4 mm long, glabrous, apex obtuse, minutely apiculate. Carpels numerous, up to 60 per flower; ovaries pubescent; styles 8-12 mm long, densely villous. Achenes laterally compressed, elliptic, ca. 3.9 × 2.1 mm, puberulous; persistent styles 6.5 cm long, plumose.
Specimens seen (paratypes   Habitat and conservation status. According to currently available data regarding C. mae, it occurs only in its type locality. The environment of the habitat is stable. We found about 200 individuals of the new species scattered along the river bank (elevation ca. 2500-2600 m) of Yuer Gou, Toksun Co. and we did not find individuals of this species outside this area. The herbarium investigation showed that several C. sect. Meclatis specimens were collected in Toksun Co., e.g. AJ Li & JN Zhu 7288,   IUCN 2012). Etymology. The species epithet is chosen in honour of the collector, Ms. Ma Ming, who first noticed this new species and guided the last author to collect specimens.
Taxonomic notes. The new species clearly belongs to sect. Meclatis by its ascending sepals and pubescent and linear-lanceolate stamen filaments (Tamura 1995, Wang 2006 and is more similar to C. glauca than to C. orientalis. Observations of hairs, leaflets, flower size and shape and other characteristics clearly demonstrate that the new species is a taxonomic entity distinct from C. orientalis. Clematis orientalis is one of the most widely distributed species in its genus and has a wide range of morphological variation (Grey-Wilson 1989, Brandenburg 2000, Wang 2006). Both Grey-Wilson (1989) and Wang (2006) recognised seven varieties. The leaf shape of C. orientalis is strikingly variable (summarised by Grey-Wilson 1989) and may be similar to that of C. mae, but the leaves of C. mae are thinner than those of C. orientalis. Moreover, C. orientalis is often identified by its grey leaves, hairy stems and flowers and reflexed linear-oblong sepals. Clematis mae from central Xinjiang is less hairy than C. orientalis and has larger flowers with ascending lanceolate sepals (Fig. 3). The hair and floral characteristics of the new species are somewhat similar to those of C. glauca, another widely distributed species with wider leaflets and sepals. In comparison with C. orientalis, C. glauca has less hairy stems and flowers, much wider leaflets and sepals and non-reflexed sepals. The primary differences between the new species and C. glauca are their leaflet shape, sepal shape and flower shape and size. Furthermore, the bracteoles of C. glauca are sometimes 3-lobed, which is never the case in C. mae.